Field of the Invention
The present invention relates to a seat belt retractor capable of winding a webbing of a seat belt on a rotatable winding drum.
Related Background of the Invention
A seat belt device including a retractor is generally mounted in a vehicle such a car in order to protect an occupant seated on a seat. The occupant wears a webbing (seat belt) drawn out from a winding drum of the retractor and is restrained on the seat with the use of the webbing. As to the seat belt retractor, conventionally, a retractor capable of switching between an automatic locking retractor (ALR) state and an emergency locking retractor (ELR) state is known (refer to Patent Literature 1).
When the retractor is switched to the ALR state, the webbing cannot be drawn out and can only be wound. The ALR state is used when, for example, a child seat or luggage is fixed onto the seat. In contrast to this, when the retractor is switched to the ELR state, normally, the winding and drawing-out of the webbing are possible so as not to disturb a movement of the webbing. However, when the vehicle encounters an emergency, rotation of the winding drum in the drawing-out direction is stopped and the drawing-out of the webbing is stopped, by a locking mechanism of the retractor.
As described above, according to the conventional retractor described in the Patent Literature 1, the state of the retractor can be switched in accordance with the intended use. However, in performing a switch action when switching the retractor from the ALR state to the ELR state, the webbing is required to be wound by a predetermined length, on the winding drum. Thus, the retractor cannot be promptly switched from the ALR state to the ELR state, and from the start to the completion of the switching, the retractor is put into an unstable state. Accordingly, the occupant may be embarrassed and confused by an operation of the seat belt. Therefore, to eliminate the unstable state of the retractor, prompt switching from the ALR state to the ELR state is demanded.